Flange-type scaffold joint adapted to resist loosening of wedge in response to vibration and tapping

ABSTRACT

A releasable joint connects an upright (10) and a transverse brace (16) in an aluminum scaffold frame. A horizontal aluminum flange (12) is attached to the upright (10) and an aluminum connector (18) to the brace (16). The connector (18) has a mouth (50) which receives the flange (12). A steel wedge (20) is inserted through a vertical passage (52) in the connector (18) and an opening (28) in the flange (12). The opening (28) contains a vertical, planar wedge-seating surface (36) of uniform horizontal cross-section. The connector (18) contains a pair of parallel, planar wedge-seating surfaces (54, 56), one above and one below the flange (12). These surfaces (54, 56) extend downwardly and radially outwardly relative to the upright (10) at a predetermined angle relative to vertical and have uniform horizontal cross-sections. The wedge (20) has a vertical edge surface (64) that mates with the wedge-seating surface (36) in the opening (28) and a pair of edge surfaces (66, 68) inclined at the predetermined angle and mated with the wedge-seating surfaces (54, 56) in the connector (18). The various mated surfaces slide relative to one another as the wedge (20) is forcefully inserted or released from the joint, reducing wear. The wedge (20) also forces the connector (18) downwardly against the flange (12), during wedge (20) insertion, ensuring that the joint is reliably locked.

TECHNICAL FIELD

The invention relates generally to scaffold frames, and morespecifically, to wedge-operated joints for joining components of ascaffold frame.

BACKGROUND ART

Uprights and transverse braces are principal components of a knock-downscaffold frame. A variety of releasable joints are known that permit theprincipal components to be joined to produce a unitary structure. Thepresent invention has application to a wedge-operated joint whosegeneral configuration has been widely accepted in the scaffold industry.The joint includes an annular horizontal flange which is fixed to anupright and which has a set of openings between its upper and lowerfaces. A complementary connector is fixed to the brace and has a mouththat receives the flange. A vertical passage in the connector is alignedwith a flange opening, and a wedge is inserted through the alignedpassage and flange opening to secure the joint. The wedge acts betweenthe connector and the radial periphery of the flange to force theconnector against the upright, locking the joint. Exemplary joints ofthis nature are shown in U.S. Pat. No. 4,044,523, No. 4,394,095, No.4,426,171 and No. 4,603,756, all to Layher.

Inserting the wedge causes wear in the flange, the connector and thewedge itself. The wedge normally bears against a particular seatingsurface formed in the flange opening. In the prior Layher patents, theseating surface is rounded and the edge of the wedge that engages theseating surface is inclined relative to vertical. Since the wedge isdriven vertically, it attacks the point of contact with considerableforce, producing essentially a cutting action. Although the wedge isshaped to mate with vertical surfaces within the connector, at leastwhen fully seated, similar point contacts may be formed as the wedge isdriven to a final position or during initial stages of removal while thejoint is stressed. The resulting wear may be gradual and tolerable insteel scaffold frames but it can quickly defeat the operation of analuminum system. In that regard, it should be noted that steel wedgesare still suggested for use in aluminum systems in order to withstandthe hammering necessary to insert and remove the wedges.

Such scaffold joints also have a tendency to loosen and release. Wedgingaction inherently applies an upward force to the wedge. Point contactsbetween components may be inadequate to react such upward forces andavoid loosening of the wedge. Another significant aspect of this problemappears to have been overlooked. The connector normally rests on theupper surface of the flange when the joint is in a released state. Asthe wedge is driven downwardly, it not only forces the connectorhorizontally against the upright but also raises the connector until thelatter engages the lower surface of the flange. Vibration, striking orother dynamic loads applied to the associated brace then cause theconnector to dislodge, releasing the wedge and the joint. Moreover, aworker senses a significant resistance to wedge insertion when theconnector engages the bottom surface of the flange. A worker tends tostrike the wedge several more times assuming, incorrectly, that thewedge is just beginning to lock the joint. This encourages furtherdamage to the components of the joint and is most significant if analuminum flange is provided.

Alternative wedge-operated scaffold joints have been proposed but thesealso appear subject to the wear and loosening problems described above.U.S. Pat. No. 4,493,578 to D'Alessio proposes a wedge with one roundedside edge ostensibly conforming to vertically-aligned surfaces in theconnector. The opposing side edge of the wedge and the correspondingseating surface within the associated flange opening are both angledrelative to vertical, somewhat reducing wear. However, the angle betweenthe side edges of the wedge does not conform to the inclination of thewedge-seating surface defined by the flange. Point contacts are formed,which contribute once again to wear. Furthermore, producing awedge-seating surface that is not perpendicular to the customary flatupper surface of the flange adds complexity and increases manufacturingcosts. In U.S. Pat. No. 4,840,513 to Hacket, point contacts are formedbetween the wedge, connector, and flange at various stages of wedgeinsertion and removal, once again leading to wear. In the scaffold jointdescribed in U.S. Pat. No. 4,525,096 to Green et al, the wedge has oneedge that aligns with a corresponding vertical wedge-seating surfacewithin a flange opening, once the wedge is fully seated. However, theopposing side edge wedge is then angled relative to vertical and bearsagainst vertical surfaces in the connector. One of the verticalconnector surfaces is formed on an abutment element that displacesrelative to the rest of the connector. Once again, point contacts areformed during wedge insertion and removal, which are expected to lead towear.

DISCLOSURE OF THE INVENTION

In one aspect, the invention provides a releasable joint between anupright and a transverse brace in a scaffold frame. The joint includesan annular horizontal flange that extends radially from the upright. Theflange has an upper face, a lower face, and an opening formed betweenradially inner and outer portions of the flange and extending betweenthe flange faces. The radially outer flange portion defines awedge-seating surface within the flange opening. The wedge-seatingsurface extends vertically between the flange faces and has asubstantially uniform horizontal cross-section along a vertical axis.

A connector is attached to the brace. It comprises upper and lowerconnectors portions spaced to define a horizontal mouth that receivesthe flange. A passage extends through the upper and lower connectorportions, intersecting the connector mouth, and is aligned with theflange opening. The connector has upper and lower wedge-seating surfaceslocated respectively within the upper and lower connector portions andpositioned to a radially inner side of the passage. (Radial directionsin this specification and the appended claims should be understood asrelative to the upright.) The upper and lower wedge-seating surfaces areparallel and inclined downwardly and radially outwardly along axesinclined at a predetermined angle relative to vertical. Each has asubstantially uniform horizontal cross-section along the associatedaxis.

A wedge is inserted through the connector passage. The wedge has aradially outer side edge that defines a vertical contact surface. Thevertical contact surfaces has a substantially uniform horizontalcross-section along the vertical axis, which conforms to the horizontalcross-section of the wedge-seating surface of the flange. The verticalcontact surface and the wedge-seating surface of the flange are matedalong the vertical axis for relative sliding displacement along thevertical axis. The wedge has a radially inner side edge that definesupper and lower contact surfaces which are parallel. The upper contactsurface has a substantially uniform horizontal cross-section along thefirst axis, which conforms to the horizontal cross-section of the upperwedge-seating surface, and is mated with the upper wedge-seating surfacefor relative sliding displacement along the first axis. The lowercontact surface has a substantially uniform horizontal cross-sectionalong the second axis, which conforms to the horizontal cross-section ofthe lower wedge-seating surface, and is mated with the lowerwedge-seating surface along the second axis for relative slidingdisplacement along the second axis. A stop structure is attached to theupright and positioned to be engaged by the connector when the latter isdisplaced radially inwardly toward the upright.

When the wedge is driven vertically, the various pairs of mated surfacesslide relative to one another simultaneously along their associatedaxes. When viewed in vertical cross-section, the surfaces are contactedalong a line rather than at a point. The tendency of the wedge to cutthe flange or damage the connector is significantly reduced. Thebenefits are most pronounced when the flange is formed of analuminum-containing material and the wedge is formed of a comparativelyhard material, such as steel.

Another aspect of the joint should be noted. The wedge-seating surfacein the flange is vertical. The wedge-seating surfaces in the connectorare inclined downwardly and radially outwardly, effectively extendingunder the wedge at an angle relative to vertical. Thus, when the wedgeis hammered downwardly to lock the joint, it urges the connector towardthe upper surface of the flange. Once locked, the joint is stable andtends not to release unless the wedge is hammered from below.

Other aspects of the invention will be more apparent from a descriptionbelow of a preferred embodiment and will be more specifically defined inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood with reference to drawings inwhich:

FIG. 1 is a fragmented perspective view of a releasable scaffold jointembodying the invention;

FIG. 2 is a fragmented cross-sectional view in a vertical planeproviding further detail of the joint; and,

FIGS. 3 and 4 are fragmented elevational views in partial cross-sectionshowing a prior art scaffold joint respectively in released and lockedstates.

BEST MODE OF CARRYING OUT THE INVENTION

Reference is made to FIGS. 3 and 4 which show a prior art joint betweenan upright 80 and a horizontal brace 82 in a scaffold frame. The jointincludes a circumferential flange 84 that is welded in a horizontalorientation to the upright 80. A connector 86 is attached to the brace82 and has a mouth 88 that receives the flange 84. A wedge 90 insertsinto a vertical passage (not numbered) in the connector 86 and analigned opening 92 in the flange 84. The connector 86 has upper andlower wedge-seating surfaces 94, 96 that are vertical. These surfaces94, 96 cooperate with a vertical contact surface 98 defined by aradially inner edge of the wedge 90. The wedge 90 has another contactsurface 100 on its radially outer edge which is angled relative tovertical and engaged with a rounded surface at the opening 92.

It will be noted that the wedge 90 engages the flange 84 at an angle,which results in a cutting action as the wedge 90 is driven downwardly.Another problem with the prior art joint is highlighted in the twoviews. In FIG. 3, the joint is shown released with the connector 86resting against the top of the flange 84. Although the wedge 90 isinserted, it has not yet be driven downwardly far enough to lock thejoint and can be readily removed. As the wedge 90 is hammereddownwardly, the connector 86 is compressed against the upright 80 andsimultaneously forced upwardly until it contacts the bottom of theflange 84, substantially as shown in FIG. 4. The orientation of FIG. 4is not very stable. The joint is able to withstand static loads appliedto the brace 82, but tapping or vibration can dislodge the connector 86,causing it to drop to the upper surface of the flange 84. As theconnector 86 drops, the wedge 90 is freed, releasing the joint. Althoughthe wedge 90 is still present and will prevent the brace 82 fromimmediately disengaging from the flange 84, it will be apparent to thoseskilled in the art what hazard is posed if various joints in a largescaffold frame are released in this manner. Driving the wedge 90 anexcessive distance through the flange 84 and the connector 86 mighttypically handle the problem. The resulting deformation of jointcomponents may maintain a locked state but the deformation is permanentand repeated deformation causes the components to wear quickly. Steelwedges and flanges may endure such abuse for considerable time beforerequiring repair but flanges of aluminum-containing compositions willtend to fail more quickly.

FIG. 1 shows components of a scaffold frame that are particularlypertinent to the present invention. These include an extruded upright 10(extensively fragmented). An annular flange 12 is welded to an extrudedmounting sleeve 14, and the assembly of sleeve 14 and flange 12 is thenwelded to the upright 10 with the flange 12 in a horizontal orientation.Alignment ribs and grooves (not indicated with reference numerals) areused to set the angular orientation of the flange 12 relative to thesleeve 14 and also the sleeve 14 relative to the upright 10 prior towelding, to position flange openings but such matters are not an aspectof the present invention. A tubular transverse brace 16 is secured tothe flange 12 with a connector 18 and a wedge 20. The wedge 20 is formedof steel but the other components are relatively soft aluminumcompositions, preferably compositions containing magnesium.

The flange 12 has upper and lower planar faces 22, 24. It is formed withtwo sets of four openings that extend between the flange faces 22, 24.One set of smaller openings is equally spaced by ninety-degrees. Anopening 26 specifically indicated in FIG. 1 and another opening 28specifically indicated in FIG. 2 are exemplary. This set of openings isintended to orient braces connected to the flange 12 at right angles toone another. Each opening of the other set (such as the exemplaryopening 30 specifically identified in FIG. 1) has greatercircumferential extent and permits braces to be oriented at variousrelative angles. Such matters are well known and will not be describedfurther.

The configuration of the flange opening 28 and its relationship to theconnector 18 and brace 16 are typical. The opening 28 is formed betweenradially inner and outer portions 32, 34 of the flange 12. It ispreferable not to extend the opening 28 radially to the sleeve 14 asthis weakens the flange 12 considerably. The radially outer flangeportion 34 defines a planar wedge-seating surface 36 within the flangeopening 28. That surface 36 extends between the flange faces 22, 24 andhas a substantially uniform horizontal cross-section along a verticalaxis 37.

The connector 18 is integrally cast. It has upper and lower connectorportions 38, 40 that are rigidly fixed to one another through a circularbase 42. A stem 44 extends from the base 42 into one end of the brace16. The stem 44 is cast with a pair of longitudinal grooves (such as thegroove 46) that interlock with a pair of ribs (such as the rib 48)extruded with the interior of the brace 16. This ensures that theconnector 18 remains in a predetermined orientation relative to acorresponding connector (not illustrated) at an opposing end of thebrace 16 to permit simultaneous joining of the brace 16 to two flangeson separate uprights. The connector 18 is welded (not shown) to thebrace 16 in its set angular orientation. The stem 44 is significant asit better reacts shearing forces and torques arising at the joint.

The connector portions 38, 40 are vertically spaced to define ahorizontal mouth 50 that receives the flange 12. A vertical passage 52extends fully through the upper and lower connector portions 38, 40,intersecting the mouth 50. It is aligned with the flange opening 28 forreceipt of the wedge 20. Both the passage 52 and flange opening 28 aredimensioned to loosely receive the wedge 20. The connector 18 has planarupper and lower wedge-seating surface 54, 56 (which are interruptedcentrally by horizontal passages that allow debris from any stop engagedby the connector 18 to escape through the interior of the connector 18).The surfaces 54, 56 are formed in the connector passage 52 on itsradially inner side. The upper and lower wedge-seating surfaces 54, 56are parallel and extend downwardly and radially outwardly along parallelaxes 57, 58 which are inclined at about 7 degrees relative to vertical.The axes 57, 58 are coincident but that is not strictly necessary forpurposes of the invention. The surfaces 54, 56 have substantiallyuniform horizontal cross-sections along the axes 57, 58.

The wedge 20 tapers from top to bottom in overall configuration. It hasradially inner and outer side edges 60, 62. The radially outer side edge62 defines a vertical contact surface 64 that has a substantiallyuniform flat cross-section along the vertical axis 37 conforming to thatof the vertical wedge-seating surface 36 of the flange 12. The radiallyinner side edge 60 defines upper and lower parallel, planar contactsurfaces 66, 68 that are separated by an intermediate surface 70. Theupper and lower contact surfaces 66, 68 are inclined at the same angleof 7 degrees relative to vertical as are the upper and lowerwedge-seating surfaces 54, 56 of the connector 18. They havesubstantially uniform horizontal cross-sections conforming along theaxes 57, 58 to the cross-sections of the wedge-seating surfaces 54, 56.The intermediate surface 70 is spaced radially outwardly from the innerflange portion 32 to avoid interference with wedging action. It is notnecessary, however, to form an indented intermediate surface 70 if theopening 28 is radially dimensioned as shown. The upper and lower contactsurfaces 54, 56 may in fact be part of a single flat edge surface.

In this embodiment, the sleeve 14 serves as a stop structure in generalradial alignment with the flange opening 28. The connector 18 must bedriven radially inwardly toward the sleeve 14 and compressed against thesleeve 14 to lock the joint properly. As in the prior art, tapping thewedge 20 downwardly through the passage drives the connector 18 againstthe stop structure. Tapping the wedge 20 upwardly releases the connector18 from the stop structure. The connector 18 will normally be very closeto the sleeve 14 even when the joint is released. The wedge 20 thustravels a short vertical distance (typically about 5 mm.) either to lockto or release the joint. Once the joint is released, the wedge 20 may befreely removed.

Three pairs of mated surfaces are present. A first pair consists of thevertical surfaces 36, 64 of the flange 12 and the wedge 20 which aremated along the axis 37. A second pair consists of the upperwedge-seating surface 54 of the connector 18 and the upper contactsurface 66 of the wedge 20 which are mated along the axis 57. The thirdpair consists of the lower wedge-seating surface 56 of the connector 18and the lower contact surface 68 of the wedge 20 which are mated alongthe axis 58. As the wedge 20 is driven vertically to and from theorientation of FIG. 2, the paired surfaces slide relative to one anotheralong their respective axes 37, 57, 58. The parallel relationshipbetween the second and third pairs of mated surfaces and their commonangle relative to vertical preserves their mated relationships inresponse to vertical displacement of the wedge 20. Use of uniform,conforming cross-sections allows relative sliding along the axes 37, 57,58.

The force applied to the connector 18 during insertion of the wedge 20is shown diagrammatically in FIG. 2. It resolves into a horizontalcomponent 72 that drives the connector 18 against the upright 10 and adownward vertical component 74 that drives the connector 18 against theupper face 22 of the flange 12. The downward component 74 isattributable to the inclination of the wedge-seating surfaces 54, 56within the connector 18, downwardly and radially outwardly, and to thesubstantially vertical orientation of the wedge-seating surface 36within the flange opening 28.

It will be appreciated that a particular embodiment of the invention hasbeen illustrated and that various modifications may be made withoutnecessarily departing from the scope of the appended claims. Forexample, planar seating and contacting surfaces are preferred forsimplicity of manufacture. However, that is not critical to broaderaspects of the invention. Mated surfaces need only have complementaryhorizontal cross-sections that are sufficiently uniform as to permitreliable sliding while mated.

I claim:
 1. In a scaffold frame comprising a releasable joint between anupright and a transverse brace; the joint comprising a horizontalannular flange centered about and encircling the upright and extendingradially from the upright, the flange comprising an upper face, a lowerface and an opening located between radially inner and outer portions ofthe flange and extending between the faces; the joint further comprisinga connector attached to the brace, the connector comprising upper andlower connector portions spaced to define a horizontal mouth thatreceives the flange, a passage extending through the upper and lowerconnector portions, intersecting the mouth and aligned with the opening;the joint further comprising a wedge inserted through the passage andthe opening and removable upward through the passage; an improvementadapted to resist releasing of the wedge in an upward direction relativeto the connector in response to vibration or tapping of the joint, inwhich:the flange comprises a wedge-seating surface which is aligned witha vertical axis and has a uniform horizontal cross-section along thevertical axis, the wedge-seating surface defined in the opening of theflange by the radially outer flange portion and extending between thefaces of the flange; the connector comprises an upper wedge-seatingsurface located within the upper connector portion on a radially innerside of the passage, and a lower wedge-seating surface located withinthe lower connector portion on the radially inner side of the passage,the upper and lower wedge-seating surfaces of the connector areparallel, the upper wedge-seating surface extends downward and radiallyoutward along a first axis inclined at a predetermined angle relative tothe vertical axis and has a substantially uniform horizontalcross-section along the first axis, the lower wedge-seating surfaceextends downward and radially outward along a second axis inclined atthe predetermined angle relative to the vertical axis and has asubstantially uniform horizontal cross-section along the second axis;and, the wedge comprises a radially outer side edge defining a verticalcontact surface extending along the vertical axis, the vertical contactsurface has a substantially uniform horizontal cross-section along thevertical axis which conforms to the horizontal cross-section of thewedge-seating surface of the flange such that the vertical contactsurface and the wedge-seating surface of the flange mate along thevertical axis for relative sliding displacement along the vertical axis;and, the wedge comprises a radially inner side edge defining an uppercontact surface and a lower contact surface, the upper and lower contactsurfaces extend downward and radially outward along the first and secondaxes respectively, the upper contact surface has a substantially uniformhorizontal cross-section along the first axis which conforms to thehorizontal cross-section of the upper wedge-seating surface such thatthe upper contact surfaces is mated along the first axis with the upperwedge-seating surface for relative sliding displacement along the firstaxis, the lower contact surface has a substantially uniform horizontalcross-section along the second axis which conforms to the horizontalcross-section of the lower wedge-seating surface such that the lowercontact surface and the lower wedge-seating surface mate along thesecond axis for relative sliding displacement along the second axis;whereby, during insertion of the wedge downward through the passage ofthe connector and the aligned opening of the flange, the wedge forcesthe connector downward until the upper connector portion seats on theupper face of the flange thereby preventing releasing of the wedge. 2.The scaffold frame of claim 1 in which the wedge-seating surface of theflange and each of the upper and lower wedge-seating surfaces of theconnector are planar.
 3. The scaffold frame of claim 2 in which theflange is formed of an aluminum-containing composition and the wedge isformed of steel.
 4. The scaffold frame of claim 3 in which the connectoris formed of an aluminum-containing composition.
 5. The scaffold frameof claim 1 in which the first and second axes are coincident.